DESCRIPTION: Periodontal diseases are associated with pathogenic bacteria which colonize the subgingival area. Inflammatory responses mediated by cells of the innate immune system are critical determinants of periodontal diseases. One of the most prominent bacteria is Porphyromonas gingivalis (Pg). Periodontitis is thought to result from host tissue injury caused by the response of cells of the innate immune system, namely monocytes/macrophages and granulocytes. In recent years, the Toll-like receptors (TLR) have rapidly emerged as a dominant route by which the innate immune system recognizes microbial pathogens. TLR activation requires a host of intracellular adaptor proteins proximal to the TLRs, including MyD88, TRAF6, MD-2 and TRAM. More recently, we have identified a family of proteins that further modulate TLR signaling, called the CATERPILLER proteins. Two of these, Monarch-1 and CIAS/cryopyrin, are novel inhibitors of NF-kappaB, AP-1 and cytokine production. Nevertheless, the function of these two proteins is dependent on a modifier protein ASC (Apoptotic Speck protein with a CARD), which subverts their negative function, and causes a pro-inflammatory phenotype. The purpose of this application is to understand the roles of TLRs, their adaptors, CATERPILLER proteins and ASC during a Pg infection. Comparisons of host response to Pg vs. E. coli will be made to assess if Pg elicits unique host responses. Accordingly, the Aims are: 1) to determine which TLR molecules and their downstream mediators are important to signal host responses to Pg vs. E. coli. This will be achieved by using RNA interference technology to target human TLRs and TLR adaptor genes;we will determine if the removal of these genes causes alterations in host response to Pg as measured by cytokine responses, and by gene expression profile. 2) Monocytic/macrophage cell lines that lack Monarch-1 will be similarly tested as in 1). Since Monarch-1 appears to be an inhibitory molecule of the NF-kB and AP-1 pathway, and can modulate cytokine production, we posit that the absence of Monarch-1 may favor a more vigorous pro-inflammatory response. 3) Cell lines that lack or overexpress CIAS/cryopyrin, another modulator of inflammatory response will be similarly tested. 4) Cell lines with reduced ASC will also be tested. Since ASC can overcome the negative regulatory function of Monarch-1 and CIAS, ASC may enhance immune response to Pg to contain the infection.